Aryl-substituted BIAN complexes of iron dibromide: Synthesis, X-ray and electronic structure, and catalytic hydrosilylation activity

Abstract

Anhydrous iron dibromide complexes bearing bidentate α-diimine ligands ArNC(Me)(Me)CNAr and ArBIAN (BIAN=bis(imino)acenaphthene; Ar=dpp and Mes; dpp=2,6-diisopropylphenyl; Mes=2,4,6-trimethylphenyl) have been prepared and characterized by 1H NMR spectroscopy. The aryl-substituted BIAN complexes were structurally characterized by single-crystal X-ray diffraction, and their metrical parameters are consistent with a redox-innocent chelating ligand. A high-spin iron(II) electronic structure description for the ArBIAN iron complexes is supported by Mössbauer spectroscopy, solution state magnetic measurements, and quantum-chemical calculations. Upon reduction, the iron complexes promote catalytic hydrosilylation of 1-hexene with phenylsilane at 22°C. Under optimized conditions, 1 mol% of the dppBIANFeBr2 precatalyst was activated in situ to produce 1-hexylphenylsilane in high yield from a 1:1 ratio of 1-hexene:PhSiH3 in solvent-free conditions at 22°C in 24h.